1. Field of the Invention
This invention relates to micro-structures such as micro-gears, micro-optical parts, or molds for molding these micro-products manufactured by rapid prototyping, and a manufacturing method and an apparatus thereof, and more particularly relates to micro-structures obtained by laminating thin films consisting of a metal or an insulator which are patterned into sectional forms, and a manufacturing method and an apparatus thereof.
2. Description of Related Art
Rapid prototyping has been rapidly popularized recently as a method for molding three dimensional complex form products designed with the aid of a computer within a short time. Three dimensional products manufactured by rapid prototyping are used as parts models (prototype) of various apparatus to predict the suitability of operation or form of parts. This method has been mainly applied to relatively large parts having a size of several cm or larger, however, recently it has been desired to apply this method to manufacture micro-parts formed by precise working such as micro-gears and micro-optical parts. Conventional methods for manufacturing such micro-parts described hereinafter have been known.
(1) Stereolithography (referred to as xe2x80x9cconventional example 1xe2x80x9d hereinafter)
(2) Selective laser sintering (referred to as xe2x80x9cconventional example 2xe2x80x9d hereinafter)
(3) Sheet lamination (referred to as xe2x80x9cconventional example 3xe2x80x9d hereinafter)
(4) Method using thin films as starting material (referred to as xe2x80x9cconventional example 4xe2x80x9d hereinafter)
(Convention example 1)
FIG. 26 shows the conventional example 1 namely the stereolithography. In the xe2x80x9cstereolithographyxe2x80x9d, photo-curable resin 100, which is hardened by irradiation of light such as ultraviolet rays, is filled in a tank 101, a laser beam 102 scans on the surface of the tank 101 two-dimensionally to draw a form corresponding to the cross-sectional data of a three-dimensional product to harden the resin layer 100a, then a stage 103 is lowered by one layer, and this process is repeated layer by layer to form the three dimensional product comprising a plurality of resin layers 100a. Stereolithography is presented by Ikuta, Nagoya University, in a literature xe2x80x9cOPTRONICS, 1996, No. 4, p 103xe2x80x9d. According to the special stereolithography, planar form precision of 5 xcexcm and resolution in the lamination direction of 3 xcexcm can be attained by optimization of exposure conditions and optimization of resin characteristics. Stereolithography is also presented by Kawata, Osaka University, in a literature xe2x80x9cProceedings of MEMS 97, p 169xe2x80x9d. According to this stereolithography, planar form precision of 0.62 xcexcm and resolution in the lamination direction of 2.2 xcexcm can be attained by utilizing a principle of two-photon absorption phenomenon.
(Conventional example 2)
FIG. 27 shows the conventional example namely selective laser sintering. In the xe2x80x9cselective laser sinteringxe2x80x9d, powder 104 is laid to form a thin layer (powder layer) 104a a laser beam 102 is applied to the powder layer 104a to form a thin layer of a desired form, and by repeating this process a three dimensional sintered product composed of a plurality of powder layers 104a is formed. According to the selective laser sintering, a three dimensional product not only of resin but also of ceramics and metals can be formed.
(Conventional example 3)
FIG. 28 shows a manufacturing apparatus used in the conventional example 3, namely the sheet lamination disclosed in Japanese Published Unexamined Patent Publication No. Hei 6-190929. In this manufacturing apparatus, when a plastic film 111 is supplied from a film feeding device 110, an adhesive coating device 120 coats photo-curable adhesive 121 evenly on the underside of the plastic film 111 to form an adhesive layer, a negative pattern exposure device 130 exposes an area of the adhesive layer excepting the area corresponding to the cross sectional form of a micro-structure to form the hardened portion and the uncured portion, this is pressed down by a press roller 141 of a photo-curing laminating device 140, the uncured portion is hardened by the light from a light source 142 and bonded to the lower plastic film 111. The rear end of the plastic film 111 is cut by a laser beam from a CO2 laser source 151, and the border of the unnecessary area of the uppermost plastic film 111 is removed by the laser. This process is repeated layer by layer to form a micro-structure. In FIG. 28, 160 represents a work device for controlling this apparatus. According to the sheet lamination, a micro-structure comprising plastic sheets is obtained.
(Conventional example 4)
FIG. 29 shows the conventional example 4, namely a manufacturing method using thin films as starting material disclosed in Japanese Published Unexamined Patent Publication No. Hei 8-127073. In this manufacturing method, as shown in the drawing (a), a photosensitive resin film 171 is formed on a substrate 170, and two processes, namely a process for forming an exposed portion 171a by exposing on an area of a desired pattern as shown in the drawing (b) and a process for forming an intermediate film 172 which prevents the resin film 171 from being mixed and prevents exposure of the lower layer, are repeated to form a multi-layer structure composed of the resin film 171 and intermediate film 172 as shown in the drawing (c), and then the exposed portion 171a shown in the drawings (b) and (c) is selectively removed by dipping it in a resin developing solution and thus a three dimensional micro-structure as shown in drawing (d) is obtained. According to this manufacturing method, the resolution in the lamination direction of xcexcm order can be attained because spin coating is applied to the resin film 171 and intermediate film 172.
However, according to the conventional example 1, namely stereolithography, this method is disadvantageous in that the resolution in the lamination direction of 1 xcexcm or smaller and the film thickness precision of 0.1 xcexcm or smaller, which is required to manufacture micro-gears and micro-optical parts, cannot be attained. In detail, because an incident light applied perpendicularly onto the layer for hardening the starting material (photosensitive resin) is used, the incident light penetrates perpendicularly from the surface through the layer with decreasing intensity due to absorption, and the intensity decreases to the level of the threshold value required for curing. The layer thickness corresponding to the threshold value is the thickness of one layer, but because of dispersion of the incident light intensity, variation of the incident light intensity with time, and dispersion of the absorption coefficient of the starting material, it is difficult to obtain high resolution.
In addition, full cure process is applied to harden completely after forming because photosensitive resin is used, in the full cure process the product shrinks 1% through several %, the shrinkage is disadvantageous and causes significant deterioration of the precision.
Furthermore, this method can be applied to only micro-structures made of relatively soft photosensitive resin, therefore, if a micro-structure is required to be made of a hard material such as a metal, the only way to manufacture the product is the molding by electroforming or injection molding using a mold of this resin. The requirement of such process is disadvantageous.
According to the conventional example 2, namely the selective laser sintering, the resolution in the lamination direction is poor because an incident light applied perpendicularly onto the layer is used as in the conventional example 1, and the shrinkage in full cure process causes deterioration of precision, and furthermore the method is disadvantageous in that a transfer process is required to manufacture micro-structures made of a hard material such as metal.
According to the conventional example 3, namely the sheet lamination, the sheet thickness is the determinant factor of the resolution in the lamination direction, the lower limit is about several tens xcexcm in view of usable sheet thickness, and it is difficult to realize the resolution in the lamination direction of 1 xcexcm.
According to the conventional example 4, namely the manufacturing method using thin films as starting material, the intermediate film (for example A1) is required in order to prevent exposure of the lower layer because an incident light applied approximately perpendicularly is used in the exposure process, this method is disadvantageous in the resolution per one layer. Though a method in which two types of photosensitive resins of different sensitive wavelengths and different solubility in solvents are laminated alternately, the respective photosensitive resins are exposed, and finally developed to form a three dimensional product in order to omit the use of the intermediate film, is disclosed in the patent, because this method is still disadvantageous in that the adhesion between resins of different solubility in solvents is poor, the strength of a completed product is low, and the dimensional precision is poor due to swelling of the photosensitive resin in the final development process. Furthermore, it is impossible to apply this method directly to hard material such as metals and insulators as in the above-mentioned stereolithography because photosensitive resin is used, and the only way is a method in which a product is used as a mold.
Accordingly, it is an object of the present invention to provide micro-structures of high dimensional precision and, particularly, high resolution in the lamination direction and a manufacturing method and an apparatus thereof.
It is another object of the present invention to provide micro-structures which are formed directly of metals or insulators such as ceramics and a manufacturing method thereof and an apparatus therefor.
It is yet another object of the present invention to provide micro-structures which can be formed together from a plurality of combined structural elements and a manufacturing method and an apparatus thereof.
To achieve the above-mentioned object, the present invention provides a micro-structure comprising a plurality of laminated thin films having prescribed two-dimensionally patterned forms.
To achieve the above-mentioned object, the present invention provides a manufacturing method of micro-structures composed of a first step for forming a plurality of thin films having prescribed two-dimensionally patterned forms on a substrate, and a second step for forming the micro-structure by separating the plurality of thin films from the substrate and subsequently by laminating and bonding the plurality of thin films on a stage.
To achieve the above-mentioned object, the present invention provides a manufacturing method of micro-structures including;
a first step for forming a plurality of first thin films having a prescribed two-dimensional pattern on a substrate, and forming a plurality of second thin films composed of different material from that of the first thin films and having the same film thickness as the first thin film to form a plurality of composite thin films comprising the first thin films and the second thin films,
a second step for forming a laminate including a micro-structure by laminating and bonding the plurality of composite thin films on a stage, and
a third step for removing the first thin films or the second thin films out of the substrate to obtain the micro-structure.
To achieve the above-mentioned object, the present invention provides a manufacturing method of micro-structures including;
a first step for forming a thin film respectively on a plurality of substrates and forming a plurality of latent images having a prescribed two-dimensional pattern on each thin film formed on the plurality of substrates,
a second step for bonding the thin films each other on which the latent images are formed,
a third step for removing one substrate out of a pair of substrates having the thin films bonded each other,
a fourth step for laminating a plurality of thin films by repeating the second step and the third step, and
a fifth step for developing the latent images out of the plurality of laminated thin films.
To achieve the above-mentioned object, the present invention provides a manufacturing apparatus of micro-structures provided with;
a substrate holder having a substrate on which a plurality of thin films are formed thereon having a prescribed two-dimensional pattern provided in a vacuum chamber,
a stage disposed facing the substrate holder in the vacuum chamber for supporting a three-dimensional structure formed by laminating the plurality of thin films,
a moving means for transferring at least either of the substrate holder and the stage to position the stage successively on the plurality of thin films, and
a control means for controlling the moving means to separate the plurality of thin films from the substrate, to laminate and bond the plurality of thin films on the stage so as to form a micro-structure.